Monthly Notifiable Disease Surveillance Report - May 2018

Saturday 23rd February 2019

Key notifiable disease trends

Cryptosporidiosis: 179 cases (including two under investigation) of cryptosporidiosis were notified in May 2018, compared with 82 cases in May 2017. The highest number of cases were from Waitemata (28 cases), Capital & Coast (27) and Auckland (22) DHBs. Children aged 1–9 years accounted for 35.7% of cases and adults aged 20–39 accounted for 34.1% of cases. One Cryptosporidium outbreak was reported in May 2018, involving 12 cases at a childcare centre in Capital & Coast DHB.The usual seasonal peak for cryptosporidiosis is in spring (Figure 1) and is largely due to calving and lambing season. An autumn cryptosporidiosis peak may be due to increased recreational water use, swimming, outdoor activities and increased person-to-person spread. Additionally, labs servicing Wellington region and several other DHBS have changed their testing methodology and now screen all faecal specimens for cryptosporidiosis using a highly sensitive test called PCR. This is likely to account for at least part of this increase. More information can be found in the 2016 Annual notifiable disease report commentary. The last time New Zealand experienced an autumn increase in cases was in 2013.

Measles: One confirmed case of measles was notified in May 2018. The case was part of an outbreak associated with Christchurch and Queenstown airports, bringing the total number of confirmed outbreak cases to 16. More information on the outbreak can be found in the April Monthly Notifiable Disease Report.

Meningococcal Disease: 39 cases of meningococcal disease were notified from January to May 2018, compared with 22 cases for the same period in 2017. Ten cases were identified as group W compared with one group W case for the same period in 2017. A marked increase in group W cases has been reported in Australia since 2014 and in the United Kingdom since 2012. More information can be found in the March 2018 NZ Public Health Surveillance Report and in this immunisation update.

Pertussis: 204 cases of pertussis were notified in May 2018, consisting of 110 confirmed, 65 probable, 13 suspect and 16 under investigation cases, compared with 130 cases in May 2017. While pertussis cases have been decreasing since the peak in January 2018, this is not unusual in autumn and cases may increase again as occurred in 2012 during the last national outbreak period (Figure 2). For more information see the Monthly Pertussis Report.

Rheumatic fever: 27 cases (17 confirmed, 4 probable, 3 suspect and 3 under investigation) were notified in May 2018, compared with 17 in May 2017. 24 cases were initial episodes and 3 were recurrent episodes. Over half the cases were from Counties Manukau DHB (14 cases). For further information on rheumatic fever see the Rheumatic Fever Biannual Report and the Ministry of Health's Reducing Rheumatic Fever webpage.

VTEC/STEC infection: 86 VTEC/STEC cases (73 confirmed and 13 under investigation) were notified in May 2018, a statistically significant increase compared with May 2017 (52 cases). This increase has been ongoing since early 2016 and is partly due to changes in laboratory testing practices, with increasingly sensitive tests used for the detection of STEC and a change in practice so that all faecal specimens are screened in many labs. For further information see the 2016 Annual Notifiable Disease Report Commentary.

Histamine (scombroid) fish poisoning: An outbreak due to histamine (scombroid) fish poisoning was reported in May 2018 and involved three cases who ate a tuna entrée from a food outlet.

Influenza: An influenza A outbreak was reported in May 2018 involving four cases at a hospital (acute care). One of the cases died.

Norovirus: Twelve norovirus outbreaks (5 final and 7 interim) were reported in May 2018, involving 380 total cases. This is similar to the number of norovirus outbreaks reported in May 2017 (13 outbreaks) although a higher number of cases have been reported (244 total cases in May 2017).

The 12 norovirus outbreaks occurred involving long term care facilities (5 outbreaks), childcare centres (3), schools (2), a hospital (acute care) and a hostel/boarding house (1 each). More information on norovirus, including steps to help prevent spread of the disease, can be found on the Ministry of Health's Norovirus webpage.

Typhoid Fever: An outbreak of typhoid involving four confirmed typhoid cases with close family connections was reported in May 2018. Infection of the source case is thought to have occurred in Samoa. S. Typhi phage type E9 variant has been identified in all four cases. This phage type has been seen previously in cases with a travel history to Asian and Pacific countries including: India, Pakistan, Kiribati and Samoa.